Pump dispensers having a pump mounted on a container of product are widely used for dispensing fluid products (liquids, creams, pastes) such as medicaments, bathroom products and cosmetics.
Usually the pump body comprises a cylinder as a fixed component. A piston may be on the inner end of the plunger, whose outer manually-engageable end projects from an opening in the body, and which is reciprocable in a pumping stroke to alter the volume of the pump chamber. Therefore, dispenser pumps are typically of a kind in which the pump chamber is defined between a piston and a cylinder. Liquid product enters the pump chamber through a valved inlet and leaves it through an outlet—usually also valved—leading along an outlet channel to a discharge opening. Commonly used valves include ball and flap valves.
Conventionally the plunger projects upwardly from the top of the pump body and the pump chamber inlet is at the bottom of the pump body, drawing product by suction from the container interior beneath. So, for convenience herein the expressions “top”, “upper” etc. are used to refer to positions and directions towards the extended direction of the plunger, and “bottom”, “downwards” etc are used analogously to refer to the opposite direction/position, although this particular orientation is not essential. The dispenser is preferably of a hand-held type, used generally upright.
Usually the pump body comprises a generally cylindrical portion constituting the cylinder in which the piston works. The pump components are typically of moulded plastics materials. A pump spring is usually provided to urge the plunger towards an extended position. Many hand-operated dispensers are of the “movable nozzle” type in which the outlet, outlet channel and discharge opening are in the plunger component. Others are of the “fixed nozzle” type in which the outlet from the pump chamber, like the inlet, is part of the pump body so that the discharge channel and discharge opening need not move when the plunger is operated. The present proposals are applicable to pump dispensers of both kinds, but fixed nozzle is preferred.
The present proposals are especially relevant for dispensers of the “airless” type, in which the internal product chamber volume of the container which supplies the pump reduces as product is dispensed, so that remaining product is not exposed to air. Such dispensers may use collapsible containers, collapsible container liners or containers with a follower piston which moves up the container behind the mass of product as its volume progressively decreases. They are used when the fluid product is sensitive to oxidation or to airborne contamination.
Measures are usually taken to avoid trapping air in the container when an airless dispenser is filled and assembled.
In some cases the pump structure and assembly process provide for air to escape through the pump itself, e.g. through the dispensing path or through a vent structure, as the pump module is fixed in place onto the filled container. For example EP-A-1015341 (U.S. Pat. No. 6,240,979) has a pump with a wide tubular chimney extending down around the pump inlet. The container is filled sufficiently that, when the pump module is pushed down into place, product is displaced upwardly to fill the pump chamber. Other dispensers providing for venting of residual air are seen in EP2153908A and EP2095882A, also our EP2353727. In these, air reaches an enclosed trap or collecting space in the upper part of the structure to prevent its getting back into the container space. Another known approach shapes the bottom of the pump module to promote escape of air through the annular gap between the container neck edge and the pump body as they are pushed together. See e.g. our EP-A-1629900 in which the bottom of the pump module (with a central inlet opening for the pump chamber) forms a deep central floor with a steeply upwardly-inclined peripheral wall leading up to snap formations which lock into the container neck. The bottom of the pump module dips into the product as the pump module is pushed in, displacing air through the narrow peripheral clearance as they move towards engagement.
We have noted that the effectiveness of different structures and procedures for eliminating trapped air varies with the viscosity of the product. With viscous products, there is less flow and slower movement of bubbles. A positive displacement action (e.g. dipping of the pump module) then helps to expel air, but this happens only on assembly. Conversely, in designs which trap or sequester air within the dispenser to keep it away from the pump inlet, there is a risk with lower viscosity fluids that air finds its way back into the container interior.
One aspect of our present proposals is to provide pump dispensers adapted to eliminate or avoid air trapping, especially when relatively fluid (lower viscosity) products are packaged. A particular context for the proposals is in dosing dispensers, such as for the direct oral administration of products such as medicines, e.g. medicines for children. In this context accurate dosing and confidence in accurate dosing are of high importance.
Typically pump modules comprise the pump itself (body and plunger, usually defining a piston and cylinder between them) and an outwardly-extending adapter component which is shaped and dimensioned to fit and fix into or onto the container opening to mount the pump in place and close the container top. The adapter may be integral with the pump module, or discrete but fixed to it e.g. by snap fit. The pump module is pushed into the container opening after the container has been filled. If the product is over-filled (and some variation is inevitable in practice) there is a risk of product being squeezed right out through the gap; this must be avoided. A known measure is to start the filling with the follower piston slightly displaced upwards, so that it can move down to accommodate any excess.